Context (from comment)
It is an independent Mars that is cut-off from Earth after an apocalyptic event damages most of human civilization. The technology is nearish-future and I want to keep it relatively hard sci-fi. What I am looking for is just suggestions to what could be possible currencies on these locations. Maybe something that is actually useful like uranium (I don't think the natural decay is too hard to handle if stored properly) or similar resources.
What means of economic exchange would be common on Mars? Would there be bartering instead? Would there be something like the gold standard but for other raw materials or resources? This is obviously a very speculative question but I would love to hear the ideas everyone else has here!